The drawback of the light-pressure drive is that it makes no difference what your previous course and speed may be; if you go inertialess in the near neighborhood of a star, its light pressure kicks you away from it like a cork hit by a stream of water.

Latterly, however, the authority of Arrhenius of Stockholm has lent vogue to a "light-pressure" hypothesis, according to which, cometary appendages are formed of particles driven from the sun by the mechanical stress of his radiations.

If we consider the behaviour of very small particles, it follows that the attraction due to gravitation (depending on the volume of the particle) will diminish more rapidly than the repulsion due to light-pressure (depending on the surface of the particle), as we decrease continually the size of the particle, since its volume diminishes more rapidly than its surface.